1. Field of the Invention
The invention pertains to the field of window balances. More particularly, the invention pertains to an air dam for a jam channel of a window.
2. Description of Related Art
A window assembly generally includes a window frame, at least one sash, a pair of opposing window jambs, each jamb having a channel for allowing the vertical travel of each sash, and a balance to assist with the raising and lowering of the sash to which it is attached by providing a counterbalance force to the weight of the sash.
The jambs are positioned on either side of the sash within the window frame assembly and typically form vertical jamb channels to provide a space to permit the sash shoe or carrier to traverse up and down as a sash is raised and lowered. The jamb channels are not well sealed at either their top or bottom and each forms, in effect, a “chimney” that permits air to easily flow upwardly, which compromises the insulating value of the window. Further, dust and other fine particles can enter the jamb channel with the air flow, and can ultimately deposit on the balance system, thereby increasing the force necessary to move the carrier through the channel.
In a conventional curl spring carrier, the end of the spring is attached to the wall of the jamb channel via a fastener, as shown, for example, in U.S. Pat. Nos. 5,353,548 and 5,463,793, most commonly a screw, or the spring is attached to an anchor, as shown, for example, in U.S. Pat. No. 6,990,710. As the sash is manually moved to either open or close the window, the curl spring, which may be coiled up within the carrier, either uncoils as the carrier is moved away from the point of attachment or retracts and recoils within the carrier as the carrier is moved toward the point of attachment. The opening of a window depends on the position of the sash. The upper sash opens by being moved downwardly in the jamb channel and the lower sash opens by being moved upwardly along the jamb channel. The point of attachment and whether the curl spring is coiled within the carrier or is uncoiled in the sash's “closed” position varies with window design.
Windows are subjected to manufacturing standards that mandate specific air flow-through standards for each design. For example, there are varying standards which apply depending upon which region of the country the window is scheduled to be installed. To test a window, a blower is sealably attached to the window by a common duct, usually by cutting a hole into the glass or Plexiglas pane of one of the sashes. Pressurized air is then blown through the duct and any leaks are located and recorded. The minimum standard which all windows must pass is a wind speed of 25 miles per hour (mph). Higher wind speeds must be withstood by windows being installed in many parts of the country. For example, a design pressure of 35 (DP 35), which corresponds to a wind speed of about 143 mph, is typically required for non-coastal applications. DP 55, which corresponds to a wind speed of about 180 mph, is a preferred rating for coastal applications, due to higher wind speeds. Not only must the sash panes be able to structurally withstand this high wind speed, but the various moving and interacting elements of each window frame must be built to such tolerances so as to withstand or at least minimize the effects of these wind speed standards.
Numerous attempts have been made to try to meet these aggressive wind speed standards, but they have met with only limited success. For example, even if the window holds up to the pressure generated by the wind, the amount of air passing through the jamb channels via a “chimney effect” may be detrimentally excessive. Attempts to block or alleviate these aerodynamic forces often cause unwanted side-effects, such as adding resistance to the movement of the sash, etc. There is a need in the art for an air block that substantially achieves the goal of minimizing air flow through the jamb channel, which has the ancillary benefit of substantially reducing the amount of airborne particles that accumulates within the jamb channel, while adding a minimal or no resistance to raising and lowering the window sash and the attached window balance carrier or shoe in the jamb channel.